3型碳质球粒陨石DaG 978中粗粒磷灰石的矿物学-地球化学特征及对早期太阳系蚀变流体的限定

碳质球粒陨石中的磷灰石是流体参与蚀变作用的产物，因此可以通过对磷灰石的研究来揭示碳质球粒陨石母体上流体的地球化学性质、来源及蚀变作用的时代。最近，申请人在一块独特的未分群3 型碳质球粒陨石Dar al Gani (DaG) 978 中发现了大量具有不同产状的粗粒磷灰石。本项目拟使用多种原位分析技术对DaG 978 中的粗粒磷灰石及其共生矿物进行系统的岩相学、矿物学、稀土元素地球化学、氢氧同位素组成、Pb/Pb年龄和36Cl-36S同位素体系研究。通过粗粒磷灰石和共生矿物的矿物学特征、稀土地球化学和氧同位素组成研究揭示碳质球粒陨石中粗粒磷灰石的成因机制；通过氢同位素组成研究揭示其流体的地球化学特征和来源；通过U-Pb同位素体系研究揭示蚀变发生的绝对时间；通过36Cl-36S同位素体系研究探索36Cl曾在碳质球粒陨石磷灰石中存在的证据。本项目对限定类地行星流体的地球化学性质和来源也有重要意义。

Apatite in carbonaceous chondrites is a secondary mineral involving fluids and can provide clues for constraining the geochemical features and source of the fluids, and the time of alteration. Recently, we observed abundant coarse apatite grains with variable occurrences in an ungrouped type 3 carbonaceous chondrite Dar al Gani (DaG) 978. In this project, we will study the petrography, mineralogy, rare-earth-element geochemistry, hydrogen and oxygen isotopic compositions, Pb/Pb age, and 36Cl-36S systematics of these coarse apatite grains. Based on the data of mineralogy,REE geochemistry, and oxygen isotopic compositions, we can constrain the origin of the coarse-grained apatite in DaG 978.Based on data of hydrogen isotopic compositions, we will constrain the geochemical features and sources of alteration fluids on the parent bodies of meteorites. We will constrain the absolute age that the alteration took place based on the Pb/Pb ages of apatite grains in DaG 978. The 36Cl-36S data will provide an important opportunity to find a record of 36Cl when the coarse-grained apatite formed.The results of this project will also have significant implications for understanding the geochemical features and sources of fluids on the surfaces of terrestrial planets and asteroids.